A mixer circuit is an important building block in, for example, radio transceivers and radar systems, and is usually used to shift a Radio Frequency, RF, signal into an Intermediate Frequency, IF, signal or vice versa. Important parameters in a mixer circuit are, for example, conversion gain, linearity and noise figure, as well as the isolation between different ports of the mixer circuit.
One particular group of mixers are so called active mixers, which comprise such types of mixers as “square law” mixers and “single balanced” mixers.
The square law mixer has a good linearity performance, but has a need for a rather large so called LO, local oscillator, power input, and can also sometimes exhibit an undesirably high noise figure and a low conversion gain. In single balanced mixers, a problem which can occur is poor linearity.